The culture wars do not end. They only change their shape and move to different battlefields.

That is one conclusion that could be drawn by the renewed battle over abortion that has arisen in two states that have passed laws representing a serious infringement on women’s reproductive rights.

First, the Arkansas legislature overrode the veto of Democratic Gov. Mike Beebe last month to impose a new limit that would ban most abortions after the 12th week of pregnancy.

In Roe v. Wade the Supreme Court set the limit for legal abortions at the point when a fetus could survive outside the womb — or 22 to 24 weeks.

Then last week Gov. Jack Dalrymple of North Dakota signed a law that banned abortions after the point when a fetal heartbeat can be detected — or about six weeks.

Even Dalrymple acknowledged that the chances the North Dakota law would survive legal challenge were questionable. So why have the legislatures of these two conservative states decided that now was the time to make a frontal assault on Roe v. Wade?

An article in The New York Times on Sunday offered a clue. It described the thinking that went into the decision by the Supreme Court to take up the two gay marriage cases that came before the court last week. The court was not required to hear the cases. But the reporter’s analysis of the justices’ questions and comments during oral arguments suggested that Justice Antonin Scalia had concluded it was now or never for defending bans on same-sex marriage. That’s because the tide of public opinion was running strongly in the other direction.

The action in Arkansas and North Dakota may reflect a similar sense among conservatives: American society, after the re-election of President Obama, is drifting to the left, and it is time now to make a stand.

There are few signs that public opinion favors making abortions illegal. Last November two Republican Senate candidates torpedoed their own races with bizarre comments about abortion and rape. These were not nuanced views on fetal viability. These were over-the-top, patronizing, ignorant comments by men about the lives of women, and the candidates paid the price.

But the weirdness of those comments suggests that the anti-abortion elements within the Republican Party have been driven to assert views that are increasingly extreme in order to try to withstand the liberal tide that appears to be on the rise.

That tide can be seen in the shift of public opinion on same-sex marriage. Republican electoral defeats and the sense that the party is out of touch with young voters have persuaded some leading Republicans to give up on the fight to resist gay marriage. That shift could have been behind an effort by Justice Scalia to enable the Supreme Court to lay down a marker preserving states’ rights to limit gay marriage.

And so Arkansas and North Dakota may have decided it’s now or never in challenging the strictures of Roe v. Wade, shrinking the period when a pregnant woman may be allowed to exercise the right to choose abortion from about six months down to three or one and a half.

We ought to remind ourselves that the court found that a woman’s right to privacy embraced the right to make medical decisions without the interference of the state, as long as the fetus had not reached the point of viability. The dispute about the status of the fetus and whether or when it embodies human life deserving of protection remains at the heart of the abortion debate. It is a question suffused with religious implications, which is why it is at the heart of a cultural divide that we cannot expect to be bridged anytime soon.

But the more liberal view taken by voters who have elected candidates willing to let women choose may have inspired the more extreme efforts by states where conservative legislators are seeking to make a last stand. Except no stand in these battles seems really to be a last stand, and we can expect the battle to go on.